A prior art endoprosthesis is shown in a publication entitled "Endoprothesen-System nach Prof. Mittelmeier" issued by OSTEO AG of Selzach, Switzerland. This endoprosthesis comprises a shank insertable essentially over its full length into a patients thighbone and evincing a conical adapter at its free end to receive a ballhead with a matching conical recess. Ballheads of different configurations may be affixed to the conical adaptor. In particular, the various ballheads evince different outside diameters with the conical recesses shown mounted at different axial distances relative to the ballhead. The above assembly permits matching of the ballhead position to the adapter and hence to the shank and the thighbone.
The above endoprosthesis system incurs the drawback whereby several ballheads having different locations of the conical recess relative to the center of the ballhead must be stocked in order to be able to match the ballhead position relative to the adapter and hence the shank, depending upon the particular needs of the patient. Stocking of ballheads is cumbersome as well as costly. Moreover matching of the ballheads is only roughly possible if ballhead stocking is kept within bounds.